Extending Sleep to Improve Glycemia in Pediatric Type 1 Diabetes RDK110528-A Project Abstract Data have increasingly supported the association of sleep and metabolic functioning. We previously found that various sleep parameters are associated with glucose control and psychosocial functioning. Unfortunately, sleep is not routinely addressed in standard clinical care for youth with type 1 diabetes mellitus (T1DM). An experimental study is needed to verify the direct impact of sleep duration on glycemic control and neurobehavioral functioning in youth with type 1 diabetes. Therefore, our primary study aims are to (1) Test if lengthening sleep improves glycemic control and in youth with T1DM; (2) Assess if ?booster? sessions can contribute to sustained sleep length; and (3) Assess if ?booster? sessions can lead to statistically and clinically meaningful changes in HbA1c, the gold standard of glucose control. In the proposed randomized study, up to 175 youth (ages 10 through 17) with T1DM will be assigned to a Sleep Extension or a Control condition. The Sleep Extension lengthens youth's time in bed to allow for a healthy sleep duration, whereas the control condition does not impose a prescribed sleep schedule; it controls for time and attention. We will test the impact of sleep extension on key indices of glycemic control (average glucose levels and % time in range) and secondary benefits (e.g., quality of life, diabetes-related distress, and social-emotional functioning, traumatic stress symptoms); examine the mediating role of adherence, and explore physiological pathways of effect (e.g., heart rate variability (HRV), cortisol levels) Once our aims are achieved and a causal link is established, the proposed Sleep Extension intervention will advance knowledge about the role of sleep in diabetes management and provide a beneficial intervention to help youth with T1DM.